In the field of applying magnetic resonance imaging methods for the purposes of cardiology, it is known that a magnetic resonance image usually cannot be acquired during one single heart cycle but by repetitive acquisition of magnetic resonance signals, wherein the repetitive acquisition is synchronized to a cyclic movement of the heart.
For instance, the synchronization of the repetitive acquisition of magnetic resonance signals can be conducted with respect to the prominent R-wave of the QRS-complex of an electrocardiogram signal to ensure that each portion of the magnetic resonance image is acquired at the same phase of the cardiac cycle. However, sources of noise, such as magneto-hydrodynamic effects and magnetic gradient field distortions, give rise to synchronization issues.
To overcome these issues, it has been proposed in EP 0 925 019 B1 to determine an acquisition period of the magnetic resonance imaging system from a vector cardiogram obtained from the measurement of electrocardiogram data, by comparing an actual value of a discriminating function of the vector cardiogram, which is based on an angular relationship between the determined electrical axis of the heart and an instantaneous vector of the vector cardiogram, and a predetermined reference function. In one embodiment described in EP 0 925 019 B1, the discriminating function is defined as the scalar product of the instantaneous vector of the vector cardiogram and the electrical axis of the heart. The predetermined reference function may be a fixed threshold of a maximum amplitude of the discrimination function.
US2007/0092123A1 describes a method and device for movement correction when imaging the heart. From measured vector cardiograms a variation in the spatial position of the heart between heart periods is calculated. The calculated variation is taken into account when combining different pictures in order to avoid or at least reduce errors in the combined image date record that are caused by the variation in the spatial position of the heart.